1. Field of the Invention
The invention described in this specification relates to a precision aerosol divider.
2. Description of the Prior Art
When it was previously desired to calibrate aerosol mass concentration instruments usually a dust box or wind tunnel was used in the operation. A filter in the box or tunnel retained the sampled particles. The deficiency with these types of sampling devices is that difference of air velocity and inlet sizes at the mass sampling instrument input and the filter result in sampling efficiencies differences.
Another method used to calibrate mass monitoring instruments is to pass the aerosol through a common passage and then split the flow at a "Y" in the line. Each leg of the "Y" went to a different instrument -- one to the filter and one to the mass monitor. Generally, the split must be nearly 1 to 1 to ensure that the aerosol mass split is the same as the flow split and that the particle size distribution has not been altered. In addition to this limitation, where gravimetric measurements on the filter are being used as the standard, experience has shown it is more desirable to have the flow through the filter substantially larger than through the mass monitoring instrument. Our invention almost totally eliminates or substantially reduces these deficiencies of the prior art by using an isokinetic probe that is centered in the filter as will be explained hereafter.